Heat exchanger

ABSTRACT

A heat exchanger for controlling temperature of electrical or electronic components has at least one flat tube with an inlet port and outlet port. A coolant entering through the inlet port passes through multiple heat sinks located within the flat tube before exiting through the outlet port. The heat exchanger has a first heat sink coupled to the flat plate with multiple fins arranged based on a first fin configuration, a second heat sink coupled to the flat plate with multiple fins arranged based on a second fin configuration, and at least one coupling device. The heat sinks are arranged based on a position of one or more components mounted on the flat tube such that the number of heat sink fins is proportional to heating characteristics of the components mounted on the tube.

FIELD OF INVENTION

The invention generally relates to heat exchanger tubes and more particularly to flat heat exchanger tubes produced from sheet metal strips.

BACKGROUND OF THE INVENTION

Electronic/electrical components mounted on any circuit board generate heat, which must be dissipated for their proper functioning. In low power density applications, air is typically used to cool these electronic components. The use of fans, ducting and/or heatsinks to accomplish this is well understood and widely used in industry.

One conventional technique for cooling electronic components uses a liquid-cooled plate. The cold plate includes channels within it for distributing the cooling liquid, and inlets and outlets for enabling the liquid to enter and exit the cold plate. The cold plate is then mated to the electronic circuit board. The electrical components on the circuit board that touch the cold plate are thereby cooled because of their close proximity to the cooling liquid, but at no time do the electrical components actually touch the cooling liquid directly.

The fins in the conventional tube are continuous through out the length of the tube. The limitation of continuous fins is that the rate of heat transfer is limited due to the effect of boundary layer that initially develops and remains constant over the length of the tube.

Hence there exists a need for a heat exchanger tube that performs efficient heat transfer.

BRIEF DESCRIPTION OF THE INVENTION

The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification.

In one embodiment a heat exchanger for controlling temperature of electrical or electronic components is provided. The heat exchanges comprises at least one flat tube having an inlet port and an outlet port such that a fluid coolant enters the flat tube through the inlet port and exits the flat tube through the outlet port so as to pass through multiple heat sinks located within the flat tube, a first heat sink coupled to the flat plate, the first heat sink comprising multiple fins arranged based on a first fin configuration, a second heat sink coupled to the flat plate, the second heat sink comprising multiple fins arranged based on a second fin configuration and at least one coupling device configured for receiving one or more components. Further, the multiple heat sinks within the flat tube are arranged based on the position of one or more components mounted on the flat tube such that the fin densities of the heat sinks are proportional to heating characteristics of the components mounted thereon.

In another embodiment, a cold plate for fluid cooling one or more components is provided. The cold plate comprises at least one flat tube having an inlet port and an outlet port so as to allow a coolant fluid to flow through the flat tube such that the coolant fluid passes through multiple heat sinks located within the flat tube, a first heat sink coupled to the flat plate, the first heat sink comprising multiple fins arranged based on a first fin configuration and a second heat sink coupled to the flat plate, the second heat sink comprising multiple fins arranged based on a second fin configuration. Further, the first heat sink is located at a predetermined distance from the second heat sink so as to facilitate formation of multiple boundary layers in order to increase the heat transfer coefficient.

Systems and methods of varying scope are described herein. In addition to the aspects and advantages described in this summary, further aspects and advantages will become apparent by reference to the drawings and with reference to the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a heat exchanger as described in an embodiment; and

FIG. 2 shows a schematic diagram of an exemplary arrangement of heat sinks within a flat tube as described in an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments, which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense.

A heat exchanger 100 for fluid cooling various circuit components according to an embodiment of the invention is illustrated in FIG. 1. The heat exchanger 100 includes at least one flat tube 104 formed from a circular tube to have a top surface and a bottom surface that are substantially parallel and contiguously connected by rounded corners and defining an interior space. This interior space of the flat tube 104 is used for a coolant to flow through. The flat tube 104 includes a plurality of heat sinks extending into the interior space. Each of the heat sinks comprise multiple fins arranged in a certain fin configuration to form a plurality of channels inside the flat tube 104 for defining a passage for the fluid coolant there through.

In the embodiment of FIG. 1, three flat tubes 104 are connected between the inlet port 106 and the outlet port 108, however the number of flat tubes 104 can vary depending on the application. An inlet header tube accommodates one or more inlet ports 106 through which the fluid coolant enters the multiple flat tubes 104. Similarly, an outlet header tube houses one or more outlet ports 108 through which the fluid coolant exits the multiple flat tubes 104. Multiple parallel flat tubes 104 are coupled to the header tubes through brazed joints 110. The flat tubes 104 may be made from copper, aluminum, various nickel alloys, titanium, graphite and like metals and composites. The coolant may be a liquid such as water or an inert gas.

The coolant passing through the flat tubes 104 absorbs the heat from the flat tube 104 walls and in convection heat transfer mode. During the process, the coolant's temperature increases. The coolant exits the heat exchanger 100 through the outlet header tube. Thus the heat generated from the components is removed from the coolant using the heat exchanger 100.

Multiple heat sinks are located within each flat tube 104. In an exemplary embodiment, a first heat sink coupled to the flat plate comprises multiple fins arranged based on a first fin configuration and a second heat sink coupled to the flat plate comprises multiple fins arranged based on a second fin configuration.

The heat exchanger 100 further comprises a base plate 102 having at least one slot configured to support the at least one flat tube 104. The base plate 102 has a roughly constant, comparatively small thickness over its entire width. The cross-section of the base plate 102 is designed in the manner of a rectangle, where the long sides of the rectangle lie parallel to the tube surface. The cooling fluid enters the base plate 102 via an inlet port 106 as indicated by arrow and exits the base plate 102 via outlet port 108 as indicated schematically by arrow.

The heat exchanger 100 further comprises at least one coupling device configured for receiving one or more components. A component includes an electronic, electrical or power circuit component capable of getting heated. In one embodiment, electrical/electronic components are directly attached to the top surface of the heat exchanger 100 by glue, epoxy or other known adhesives. In another embodiment of the invention, screw attachments are attached to the top surface of the base plate 102 so that the electrical components can be conveniently attached and removed as necessary. The screw attachments may be of aluminum, copper or other like materials and compositions.

In one embodiment, the multiple heat sinks within the flat tube 104 are arranged based on the position of one or more components mounted on the flat tube 104 such that the fin densities of the heat sinks are proportional to heating characteristics of the components mounted thereon.

For example, a first circuit component that is expected to be heated to higher temperature when compared to a second circuit component positioned adjacent to the first circuit component, a first heat sink having higher fin density is positioned below the first component and a second heat sink having a comparatively lower fin density is positioned below the second component that is expected to be heated to a lower temperature. For this purpose vacuum-brazing technique is utilized. Vacuum brazing allows the use of high performance fins to be placed within the liquid channel at locations where better heat transfer is desired by the surface of the base plate 102.

In one embodiment, the second heat sink is located a predetermined distance from the first heat sink. The heat sinks are positioned such that a predetermined distance exists between two successive heat sinks inside the cold plate so as to break the boundary layers to promote the flow of the fluid coolant to be converted into turbulent flow, thereby improving heat transfer ability.

In one embodiment, the first fin configuration is selected from one of an extruded, bonded, elliptical and pin configuration. Likewise, the second fin configuration is selected from one of an extruded, bonded, elliptical and pin configuration. Accordingly, two successive heat sinks may have a similar fin configuration. Alternatively, two successive heat sinks may have varied fin configurations. An exemplary arrangement of the heat sinks having varied fin configurations is depicted in FIG. 2. In the example shown in FIG. 2, the flat tube 200 comprises seven heat sinks wherein the first heatsink has an extruded fin configuration 202, the second heatsink has a pin fin configuration 204, the third heatsink has an elliptical fin configuration 206, the fourth heatsink has a folded fin configuration 208, the fifth heatsink has an elliptical fin configuration 210, the sixth heatsink has a pin fin configuration 212 and the seventh heatsink has an extruded fin configuration 214. However, the thickness and length of the fins may vary based on the desired application of the heat exchanger 100. This arrangement of heatsinks gives rise to the flat tube 200 with increased surface area and increased turbulence.

Although, compared to a flat tube 104 having heat sink with a similar fin configuration, a flat tube 104 of this type presents advantages related to heat technology, because, for example when being operated as a cooling tube, the heat transfer characteristics for the coolant can be improved through the generation of turbulence at the intermediate portions between two successive heat sinks.

Further, each of the multiple heatsinks is manufactured from a material selected from the group comprising copper, aluminum, titanium, graphite and alloys thereof. Accordingly, two successive heatsinks may comprise same material. Alternatively, two successive heat sinks may be made up of different materials. In one exemplary embodiment, the first heatsink may comprise copper whereas the second heat sink may comprises aluminum or some other material other than copper.

In another embodiment, a method of providing internal fins to a coolant carrying tube is presented. In this method, a series of heatsinks with desired fin configurations are added as an insert to the interior space of the flat tube 104. The heat sinks are pre-applied with a brazing alloy and are positioned inside the flat tube 104 at a desired location. The heatsinks along with the flat tube 104 are then placed inside a soldering oven to get the heat sinks brazed to the inside wall of the flat tube 104. This forms a flat tube 104 with internal fins. Thus the surface area inside the flat tube 104 is increased which helps increase the heat transfer efficiency of the heat exchanger 100.

The heat exchanger 100 disclosed herein helps increase the heat transfer in the base plate 102 by increasing the surface area in the flat tube 104 and by creating turbulence in the flow at a desired area such as under a hot spot. As coolant flows from one end and leaves from other end, a heatsink with intricate fin configuration offers resistance to the flow. By optimizing the fin geometry, the desired turbulence can be created. A combination of heatsinks with different fin configuration can be positioned inside the flat tube 104 based on the heat load pattern on the base plate 102 so as to offer more surface area for heat transfer under a hot spot.

In one embodiment, the heat exchanger 100 described herein employed to cool gradient coils in an magnetic resonance imaging (MRI)) system. In the MRI system a gradient pulse amplifier applies current pulses to selected gradient coil assemblies to create magnetic field gradients in the three dimensions of the examination region. These high-powered devices generate significant thermal energy, which, if not removed, limit the device lifetime. A cold plate or heat exchanger 100 acts to remove heat from the gradient coil of the MRI system. The cold plate can effectively cool the gradient coil down to cryogenic temperatures. Thus the heat exchanger 100 helps to maintain gradient coil temperature within a specified range regardless of the selected excitation applied, thereby enabling higher power applications for faster imaging with improved image quality and longer scan times.

In one embodiment, the cold plate or heat exchanger 100 acts to remove heat from a thermally conductive side of a power semiconductor device. The thermally conductive side of the semiconductor is maintained in firm thermal contact with the heat sink by screws or other suitable affixing mechanisms.

Advantages of the heat exchanger 100 described herein include easy manufacturability, flexibility to select and arrange different type of heatsinks having varied fin configurations depending on the heat load pattern on the base plate 102 and ability to increase the heat transfer coefficient by maintaining distance between successive heatsinks within the flat tube 104.

Further, use of standard heatsinks results in decreased cost of the flat tube assembly and heatsink. As the heatsinks are readily and widely available, it is easy to source any heatsink and assemble it in the flat tube 104.

In various embodiments of the invention, a heat exchanger for cooling various circuit components is described. However, the embodiments are not limited and may be implemented in connection with different applications. The application of the invention can be extended to other areas, for example in a refrigeration apparatus, in an air conditioning system for vehicles and as a radiator for a automobiles. The design can be carried further and implemented in various forms and specifications.

This written description uses examples to describe the subject matter herein, including the best mode, and also to enable any person skilled in the art to make and use the subject matter. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 

What is claimed is:
 1. A heat exchanger comprising: at least one flat tube having an inlet port and an outlet port such that a fluid coolant enters the flat tube through the inlet port and exits the flat tube through the outlet port so as to pass through multiple heat sinks located within the flat tube; a first heat sink coupled to the flat plate, the first heat sink comprising multiple fins arranged based on a first fin configuration; a second heat sink coupled to the flat plate, the second heat sink comprising multiple fins arranged based on a second fin configuration; and at least one coupling device configured for receiving one or more components; wherein the multiple heat sinks within the flat tube are arranged based on the position of one or more components mounted on the flat tube such that the fin densities of the heat sinks are proportional to heating characteristics of the components mounted thereon.
 2. The heat exchanger of claim 1, further comprising a base plate having at least one slot configured to support the at least one flat tube.
 3. The heat exchanger of claim 1, wherein the second heat sink is located a predetermined distance from the first heat sink.
 4. The heat exchanger of claim 1, wherein the first and second fin configuration is selected from one of an extruded, bonded, elliptical and pin configuration.
 5. The heat exchanger of claim 1, wherein each of the multiple heat sinks is manufactured from a material selected from the group comprising copper, aluminum, titanium, graphite and alloys thereof.
 6. The heat exchanger of claim 5, wherein the material of first heat sink is different from the material of the second heat sink.
 7. A cold plate for fluid cooling one or more components, the cold plate comprising: at least one flat tube having an inlet port and an outlet port so as to allow a coolant fluid to flow through the flat tube such that the coolant fluid passes through multiple heat sinks located within the flat tube; a first heat sink coupled to the flat plate, the first heat sink comprising multiple fins arranged based on a first fin configuration; and a second heat sink coupled to the flat plate, the second heat sink comprising multiple fins arranged based on a second fin configuration; wherein the first heat sink is located at a predetermined distance from the second heat sink so as to facilitate formation of multiple boundary layers in order to increase the heat transfer coefficient.
 8. The cold plate of claim 7, wherein the first fin configuration is different from the second fin configuration.
 9. The cold plate of claim 7, wherein the first and second fin configuration is selected from one of an extruded, bonded, elliptical and pin configuration.
 10. The cold plate of claim 7, wherein each of the multiple heat sinks is manufactured from a material selected from the group comprising copper, aluminum, titanium, graphite and alloys thereof. 